This is a new one for me, so I thought that I'd put it out there to see if anyone else has noticed this...
My son is 19 months old now. He's easy to put to bed & takes a nap during the day regularly.
Well, his bedtime is 7:30 or 8:00. The weird thing: he wakes up at about 11:45 or 12:00ish and makes noise. He sounds like he's talking maybe moving around and sometimes a wimpy cry...he's asleep all the while. I've gone in there to check & he's sound asleep.
The only reason I've noticed this is because I've been up (insomnia) lately...
Thoughts?

My 18 mo old goes through random periods where he cries out 1-3 times a night, but most of the time it is that quick random cry and when I go in there he is fast asleep as you describe. I figure it is just something happening in their sleep cycle...just like we wake up occasionally at night, or something like that.

In our case I usually use that as a time to cover him up. He moves all over his bed, so he never keeps a blanket on himself.

My 5 year old is FAMOUS for this, and has been for as long as I can remember. She will have full on conversations with herself. :o)
As far as I know it has to do with the stage of sleep they are in. Like dreaming out loud.
I'm sure your son is doing just this, but if any other concerns arise I would mention it to your ped. just in case sleep apnea might be a cause.

I'm heading back to the pediatrician soon for well check ups & I'll ask him about it, thanks. He doesn't seem to be having issues breathing (coughing or otherwise) at night, and he seems quite rested during the day (he still takes one nap).
I've also read about children learning to talk and learning other milestones sleep talking like this. I'll find out what the doctor says and update. Thanks

My son is 2 and he occasionaly crys in his sleep as well. I remember one time he was babbling in his sleep and I asked him what sound a cow makes and he mooed!! My bigger concern is that I caought him walking in his sleep once. We now have his room gated so he can't get out.

Everyone sleeps in cycles, form lighter sleep to deep sleep and up and down. In lighter sleep a person may stir, make noise, talk etc. Toddlers sleep cycles are different from when they are babies - so you may just being seeing a shift in the cycle and he's reacting to a dream state. As you said, new milestones do effect sleep as well.

We co-slept and my DS was hilarious as a toddler - once he demanded a cookie in his sleep.

I;m confused too - is he waking and going back to sleep or making noise in his sleep?

Just an FYI most people of any age will shift around, make noise etc while asleep.